1. Field of the Invention
The invention relates to an air-conditioning system control apparatus for controlling switching of liquid accumulation process carried out when a refrigerant within a compressor of an air-conditioning system has liquefied.
2. Description of the Related Art
Commercially sold vehicles are typically equipped with air-conditioning systems. The air-conditioning systems generally include a heating function, a cooling function and a dehumidification function, and regulate the temperature, humidity and the like of air within the vehicle interior.
Air-conditioning systems are provided with a receiver tank, an evaporator, a compressor and a condenser in a cyclic refrigerant circulation pathway, and cool a vehicle interior by utilizing the vaporization heat of the refrigerant.
A refrigerant stored in the receiver tank is introduced into a pipe composing the evaporator, through which refrigerant passes. Air flowing along the outside of the evaporator pipe exchanges heat with the refrigerant. The air outside the evaporator is cooled as a result and introduced into the vehicle interior as cooled air. Conversely, the refrigerant captures the heat from the air passing through the evaporator and is vaporized. Refrigerant vaporized in the evaporator is compressed in the compressor so as to be easily liquefied. Refrigerant that has been compressed with the compressor is cooled by outside air in the condenser after which it returns to a liquid and is stored in the receiver tank. Air-conditioning systems cool the vehicle interior by repeating the circulation described above. In addition, the compressor that compresses the refrigerant as described above is operated using the output of a motive power source (such as an engine).
However, in a vehicle equipped with this type of air-conditioning system, if the vehicle is allowed to stand outdoors at a normal temperature (for example, 25° C.) for an extended period of time while the motive power engine stopped (referred to as soaking), the refrigerant within the compressor may be cooled and liquefy, causing it to accumulate in the compressor and resulting in the occurrence of what is commonly referred to as “liquid accumulation”.
When liquid accumulation occurs, there is no longer a load that has been applied to the compressor by the air-conditioning system. Because the compressor is operated utilizing the output of the motive power engine, torque intended to operate the compressor is instead output to the motive power engine, thereby resulting in revving of the motive power engine such as an engine. In response to this, vehicle air-conditioning system control apparatuses that attempt to resolve liquid accumulation in advance such as that described in Japanese Patent Application Publication No. 2005-238951 (JP-A-2005-238951).
When the vehicle air-conditioning system control apparatus described in JP-A-2005-238951 estimates that refrigerant has liquefied in the compressor when the vehicle is not in use, it activates the compressor in an attempt to eliminate liquefaction of the refrigerant. In addition, soaking time, outside air temperature, vehicle interior temperature, engine cooling water temperature and the like are used to estimate liquefaction of refrigerant when the vehicle is not in use.
However, in the apparatus described in JP-A-2005-238951, when the vehicle is not in use, namely in a vehicle that is parked with the engine stopped, a timer or temperature sensor and the like is activated to monitor the occurrence of “liquid accumulation”, and in the case “liquid accumulation” is estimated, the apparatus activates the compressor to eliminate the “liquid accumulation”. The apparatus continues to subsequently monitor the occurrence of “liquid accumulation”, and activates the compressor each time “liquid accumulation” is estimated. As a result, the compressor ends up being activated numerous times while the engine is stopped, thereby resulting in the need for a large-capacity battery. In addition, it is also not desirable to have the compressor activated automatically in a parked vehicle.
On the other hand, examples of processes carried out in response to “liquid accumulation” (to be referred to as liquid accumulation resolution processes) include processing that interrupts the transmission of rotary power from the engine to the compressor when an air-conditioning system is started, and processing that vaporizes refrigerant with an electric heater. In the case of processing that interrupts the transmission of rotary power, a prescribed torque can be maintained by discharging liquid refrigerant using the inertial rotation of the compressor, and controlling with the engine only separated from the compressor. In the case of processing that vaporizes the refrigerant with an electric heater, an electric heater is activated for a prescribed amount of time when the engine is started to vaporize liquid refrigerant.
However, because liquid accumulation resolution processing ends up being carried out regardless of the presence of “liquid accumulation” in either of the cases described above, the problem results in which time is required to start the air-conditioning system in cases in which “liquid accumulation” has not occurred. Moreover, if liquid accumulation resolution processing is carried out in cases in which “liquid accumulation” has not occurred, motive power for the compressor and electric power for the electric heater are consumed even though they are not required.